1. Field of the Invention:
The present invention relates to a tridem rear drive axle system for use in "8.times.8", or "8.times.6" or similar type vehicles. In particular, the present invention relates to a tridem rear drive axle system utilizing a transfer case having two output shafts extending to the front-rear drive axle assembly and to a front-rear drive axle assembly having two input shafts, one driving the front-rear drive axle gearing and the other connected to a through shaft drivingly connected to the middle-rear drive axle assembly.
2. Description of the Prior Art:
Tandem and tridem rear drive axle systems having two or three rear drive axle assemblies, respectively, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,000,456; 3,146,842; 3,388,760 and 3,706,350, the disclosures of which are hereby incorporated by reference. Transfer cases for transferring vehicle transmission output torque to multiple rear drive axles and/or to a front drive steer axle are known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,753,376; 3,780,821 and 2,158,320, the disclosures of which are hereby incorporated by reference. MultiPle drive axle systems wherein various so-called "torque proportioning" differentials, usually planetary type differentials, are utilized to proportion torque more advantageously between the various drive axles are also well known in the prior art. Briefly, torque proportioning differentials are those non-standard differentials which distribute input torque on other than a fifty-fifty basis to the two outputs (side gears) thereof.
While the multiple drive axle tandem and tridem rear drive axle systems of the prior art are very commercially successful and widely used, they are not totally satisfactory as substantially equal torque distribution to all of the drive axles is not provided, one of the tridem drive axle assemblies works twice as hard as the other two, elaborate and costly torque proportioning differentials in one or more of the drive axle assemblies are required, complicated and awkward vehicle drive line layouts are required and/or expensive specialized tooling, not easily justified at relatively low volumes, is required.